In the development of wireless and/or cellular communication systems, a focus is on increasing bandwidth and throughput in the radio access network, while enhancing system coverage and performance. In this regard, there are developed carrier aggregation techniques as well as heterogeneous network architectures.
A specific scenario, which is considered to be favorable in view of the above considerations, relates to inter-site carrier aggregation (CA). In the context of 3GPP standardization, i.e. the development of LTE and LTE-A, such inter-site CA scenario could equally be referred to as inter-eNB CA scenario.
In such inter-site (or inter-eNB) scenario, a terminal device such as a user equipment (UE) or the like is served by both a macro or large cell with wide-area coverage, i.e. a macro base station or eNB, and a micro or small cell with local-area coverage, i.e. a micro base station or eNB. Typically, the macro cell is used for handling control plane aspects, such as UE mobility, and the micro cell is used for offloading a large data volume and/or for extending the overall system coverage, while the macro cell and the micro cell operate on different frequencies, e.g. in different frequency bands.
The macro base station or eNB and the micro base station or eNB are located at different sites or locations, and are linked by a backhaul link. While such backhaul link could preferably be implemented without exhibiting any (significant) delay, limited capacity, etc., e.g. by an optical fiber connection, it is typically implemented exhibiting (significant) delay, limited capacity, etc., e.g. by a non-fiber connection in view of cost considerations. A non-ideal (e.g. non-fiber) backhaul link however results in an imperfect connection between macro and micro base stations or eNBs, which exhibits a non-negligible delay, e.g. of more than 1 millisecond.
In order to enable proper operation in any one of the macro and micro cells, uplink control information (UCI) may have to be separately established in both cells. For example, UCI for the macro cell may need to be transmitted in/via the macro cell, and UCI for the micro cell may need to be transmitted in/via the micro cell. This may for example be due to the fact that in/via the macro cell there may be some downlink transmission such as PDSCH, which requires CSI feedback to aid scheduling or ACK feedback for the sake of downlink HARQ.
In view thereof, one issue exemplarily arising in such inter-site (or inter-eNB) scenario relates to an UCI configuration, i.e. a configuration of UCI parameters. In particular, an appropriate UCI configuration, i.e. the configuration of UCI parameters, for the micro cell is to be achieved.
In this regard, UCI inter-cell interference might occur. While inter-cell interference coordination for UCI is currently done via Cyclic Shift Hopping to randomize the inter-cell interference, such approach may not be effective in an inter-site (or inter-eNB) scenario, especially in a scenario with a dense micro cell deployment, for example.
In view thereof, another issue exemplarily arising in such inter-site (or inter-eNB) scenario relates UCI inter-cell interference. In particular, an appropriate handling of UCI configurations is to be achieved in order to prevent or at least reduce inter-cell interference between UCI for the macro cell and UCI the micro cell.
Since layer 1 processing such as PDSCH and PUSCH scheduling may be done separately in/via the macro and micro cells, it may be not possible to have a fast inter-cell coordination to avoid concurrent transmissions in/via the macro cell and the micro cell. For example, if the UE applies power scaling on some uplink signals due to such concurrent transmissions, the eNBs in/via the macro and micro cells may not be aware of this due to the separate scheduling. The latter makes uplink detection as well as scheduling/link adaption more difficult and may impact the uplink performance, for example.
In view thereof, still another issue exemplarily arising in such inter-site (or inter-eNB) scenario relates to the difficulty in handling concurrent uplink transmissions in/via the macro cell and the micro cell. In particular, even without availability of a fast inter-cell coordination (e.g. layer 1-based coordination such as joint scheduling), an appropriate solution for concurrent uplink transmissions in/via the macro and micro cells is to be achieved.
Thus, there is a need to further improve uplink configuration and transmission control in inter-site carrier aggregation.